net/ixgbe: fix jumbo frame flag condition

[ upstream commit 48554c7 ]

The jumbo frame uses the 'RTE_ETHER_MAX_LEN' as boundary condition.
If the Ether overhead is larger than 18 when it supports VLAN tag,
that will cause the jumbo flag rx offload is wrong when MTU size is
'RTE_ETHER_MTU'.

This fix will normalize the boundary condition with 'RTE_ETHER_MTU'
and overhead even though current overhead is 18.

Fixes: 59d0ecd ("ethdev: MTU accessors")
Fixes: 95a27b3 ("net/ixgbe: enable jumbo frame for VF")

Signed-off-by: Steve Yang <stevex.yang@intel.com>
Acked-by: Jeff Guo <jia.guo@intel.com>

drivers/net/ixgbe/ixgbe_ethdev.c

@@ -5173,7 +5173,7 @@ ixgbe_dev_mtu_set(struct rte_eth_dev *dev, uint16_t mtu)
 	hlreg0 = IXGBE_READ_REG(hw, IXGBE_HLREG0);
 
 	/* switch to jumbo mode if needed */
-	if (frame_size > RTE_ETHER_MAX_LEN) {
+	if (frame_size > IXGBE_ETH_MAX_LEN) {
 		dev->data->dev_conf.rxmode.offloads |=
 			DEV_RX_OFFLOAD_JUMBO_FRAME;
 		hlreg0 |= IXGBE_HLREG0_JUMBOEN;

drivers/net/ixgbe/ixgbe_ethdev.h

@@ -104,6 +104,9 @@
 /* The overhead from MTU to max frame size. */
 #define IXGBE_ETH_OVERHEAD (RTE_ETHER_HDR_LEN + RTE_ETHER_CRC_LEN)
 
+/* The max frame size with default MTU */
+#define IXGBE_ETH_MAX_LEN  (RTE_ETHER_MTU + IXGBE_ETH_OVERHEAD)
+
 /* bit of VXLAN tunnel type | 7 bits of zeros  | 8 bits of zeros*/
 #define IXGBE_FDIR_VXLAN_TUNNEL_TYPE    0x8000
 /* bit of NVGRE tunnel type | 7 bits of zeros  | 8 bits of zeros*/

drivers/net/ixgbe/ixgbe_pf.c

@@ -575,7 +575,7 @@ ixgbe_set_vf_lpe(struct rte_eth_dev *dev, __rte_unused uint32_t vf, uint32_t *ms
 		   IXGBE_MHADD_MFS_MASK) >> IXGBE_MHADD_MFS_SHIFT;
 	if (max_frs < new_mtu) {
 		hlreg0 = IXGBE_READ_REG(hw, IXGBE_HLREG0);
-		if (new_mtu > RTE_ETHER_MAX_LEN) {
+		if (new_mtu > IXGBE_ETH_MAX_LEN) {
 			dev->data->dev_conf.rxmode.offloads |=
 				DEV_RX_OFFLOAD_JUMBO_FRAME;
 			hlreg0 |= IXGBE_HLREG0_JUMBOEN;